My prior U.S. Pat. No. 4,749,012 discloses a self-aligning cutter head assembly for delimbing trees in which curved cutting and limb stripping blades are carried by a rectangular support frame supported for pivotal movement in both vertical and horizontal planes so that the limb stripping blades are automatically maintained parallel with the longitudinal axis of the tree as the tree is pulled through the cutter head assembly by the grapple of a knuckle boom loader. In the device of my prior patent, the pivotal support in both the vertical and horizontal planes for the rectangular support frame is provided by a "fifth-wheel" connection in which both the pivot pins for providing vertical and horizontal movement are spaced close together and are both positioned beneath the rectangular support frame. While the pivotal support for the rectangular support frame in both the vertical and horizontal planes of my prior patent operates satisfactorily to maintain the limb stripping blades parallel with the longitudinal axis of the tree as it is being pulled through the cutter head assembly by the grapple of a knuckle boom loader, the close proximity of the vertical and horizontal pivot pins provided in the "fifth-wheel" connection can cause problems in certain instances. For example, if the weight of the rectangular support frame is not evenly distributed above the fifth-wheel pivotal connection, the rectangular support frame and the curved limb stripping blades carried thereby may tend to swing to a position where one portion is lower so that the cutter head is not properly aligned to receive the tree trunk at the beginning of a delimbing operation.